1. Field of the Invention
The present invention relates to irrigation and, in particular, to a system and method for automatically controlling irrigation.
2. Discussion of the Related Art
It is becoming increasingly important that irrigation controllers make efficient use of water. There have been several attempts to adjust the amount of water applied to landscape plant life based on weather conditions. Some attempts are based on mathematical models (known as evapotranspiration or ET) to determine plant watering requirements based on weather conditions. Most industry accepted ET models (such as the Penman-Monteith model) require weather data for temperature, solar radiation, humidity and wind speed. However, the sensors necessary to provide this weather data can be expensive, and as in the case of residential controllers, often cost prohibitive. Attempts have been made to create solutions that approximate the results of the ET models by storing historical ET values which are adjusted using currently sensed temperature. However, the results are often questionable since weather is not always repeatable from year to year and factors other than temperature affect ET. Others have tried alternatives to the accepted ET models in an attempt to approximate the accepted ET models. These approaches again have unproven and uncertain results.